1. Field of the Invention
The invention relates to a method for the open and/or closed-loop control of the movement of welding tongs by a welding-tong drive, which comprises at least one primary and one secondary drive device. The primary drive device moves at least two welding tong limbs with welding electrodes from essentially opposite sides towards a welding object and presses them with a predetermined contact pressure onto the object. Actuation of the secondary drive device determines a spatial orientation of the welding tongs.
2. Description of Related Art
Welding tongs are, for example, used in the production of cars to weld together metal panels as welding objects. Generally, such welding tongs comprise two welding tong limbs, which are arranged in a C or X shape. By actuating a primary drive device, the welding tong limbs are brought closer together and are finally pressed onto different sides of the welding object. The actual welding can occur spot-shaped by resistance-welding, laser-beam welding, arc welding or a similar technique.
For the welding tongs a secondary drive device is furthermore provided, through which, for example, the so-called tong compensation occurs. This prevents an unintentional change of the spatial axis of the welding tongs during movements of the complete welding device.
In addition, the secondary drive device is also used to compensate the forces arising during closure of the welding tongs and contacting of the welding object.
With previously known methods, generally a rigid welding tong limb is released or brought further towards the welding object by linear movement using air or electric motors to compensate for the forces. However, this occurs due to an uncontrolled movement of the rigid welding tong limb. For example, the contacting of the welding object by the rigid welding tong limb cannot be acquired, and in particular accurate spatial orientations of the welding object with respect to the welding tongs cannot therefore be acquired. This leads to an uncertainty during welding which conflicts with increasing quality demands for each weld.
The object of the invention is to improve a method of open and/or closed-loop control of welding tong movement such that the contacting of the welding object occurs controlled through the welding tongs and any deviations from the specified spatial points during contacting are reliably acquired.